This invention generally relates to vascular catheters and particularly to guiding catheters for the placement of intracoronary devices within a patient's vascular system such as dilatation catheters in procedures such as percutaneous transluminal coronary angioplasty (PTCA).
In the classic PTCA procedure, a guiding catheter having a preformed distal tip is percutaneously introduced into the cardiovascular system of a patient and advanced therein until the distal tip thereof is in the ostium of the desired artery. A guidewire and a dilatation catheter having a balloon on the distal end thereof are introduced through the guiding catheter with the guidewire slidably disposed within an inner lumen of the dilatation catheter. The guidewire is first advanced into the patient's coronary vasculature until the distal end of the guidewire crosses the lesion to be dilated, then the dilatation catheter is advanced over the previously introduced guidewire until the dilatation balloon is properly positioned across the lesion. Once in position across the lesion, the balloon is inflated to a predetermined size with radiopaque liquid at relatively high pressures (e.g., generally 4-12 atmospheres) to compress and split the atherosclerotic plaque of the lesion against the inside of the artery wall to thereby dilate the lumen of the diseased artery. The balloon is then deflated so that the dilatation catheter can be removed and blood flow resumed through the dilated artery.
Further details of guiding catheters, dilatation catheters, guidewires, and the like for angioplasty procedures can be found in U.S. Pat. Nos. 4,323,071 (Simpson-Robert); 4,439,185 (Lundquist); 4,468,224 (Enzmann et al.); 4,516,972 (Samson), 4,538,622 (Samson et al.); 4,582,185 (Samson); 4,616,652 (Simpson); and 4,638,805 (Powell) which are hereby incorporated herein in their entirety by reference thereto.
Frequently, sufficient force cannot be applied to the proximal end of a dilatation catheter to advance the balloon thereof across a lesion. Additional axial force can be supplied to the dilatation catheter by buttressing the guiding catheter against a wall of the aorta, by deep seating the guiding catheter tip well into the coronary ostium, by choosing a guiding catheter with a different distal configuration, or by increasing the stiffness of the guiding catheter. However, in practice, these methods are not always successful and no dilatation of a stenosis can occur unless the balloon crosses the lesion.
Steerable dilatation catheters with built-in or fixed guidewires or guiding elements are used with greater frequency because their deflated profiles are generally smaller than conventional dilatation catheters with movable guidewires having the same inflated balloon size. Moreover, the fixed guiding elements in the steerable dilatation catheters provide greater pushability which allows them to cross much tighter lesions than dilatation catheters with movable guidewires. Further details of steerable dilatation catheters may be found in U.S. Pat. Nos. 4,582,181 (Samson), 4,619,263 (Frisbie et al.), 4,641,654 (Samson et al.), and 4,664,113 (Frisbie et al.) which are hereby incorporated in their entirety by reference thereto.
While the tubular members forming the catheter body utilizing a movable guidewire could be made from stiffer material or thicker walled tubing to increase the pushability of the catheter, such added stiffness would reduce the flexibility of the distal end of the catheter which allows the catheter to pass through the tortuous passageways of a patient's vascular system.
Other types of intracoronary catheters such as those used for mechanical and laser based atherectomy procedures and angioscopic catheters generally have much stiffer shafts than balloon dilatation catheters. As a result, the guiding catheter frequently is not sufficiently strong to maintain its preformed distal shape when these stiffer catheters are disposed within the guiding catheter and advanced into and through coronary stenoses. This makes the placement of such stiffer catheters much more difficult.
In some situations, the preformed distal curvature of the guiding catheters may not be the exact curvature needed for the placement of the distal tip in the desired location within the patient's cardiovascular system.
When many of the aforesaid problems occur, the only solution is to withdraw the guiding catheter from the patient's body and replace it with a guiding catheter having a different curvature or stiffness. This recatheterization not only increases the time required for the procedure but it also adds further arterial trauma. Withdrawal of a guiding catheter necessitates withdrawing the guidewire and balloon dilatation catheter out of the coronary stenosis, which increases the risk of acute coronary closure and myocardial infarction if the coronary stenosis has not yet been properly dilated.
What has been needed and heretofore unavailable is a guiding catheter which has a distal portion or segment, the shape and stiffness of which can be changed from the proximal end after it has been inserted into the patient and which can aid in providing support to a dilatation catheter when the balloon thereof is being advanced across a tight lesion. The present invention satisfies this need.